Electrical apparatus



United States Patent 3,150,761 ELlltI'l-IRECAL APPARATUS Floyd 5. King, Willrinshurg, and Robert L. Hess, East hicleesport, Pa, assignors to Westinghouse Electric Corporation, East Pittsburgh, Pa, a corporation of Pennsylvania Filed Nov. 14, 19nd, Ser. No. 69,086 3 Claims. ((11. 174-1i) This invention relates to electrical apparatus in general and, more particularly, to electrical apparatus embodying tank structures at least partially filled with gas and associated with terminal-bushing structures.

A general object of the present invention is to provide an improved terminal-bushing structure associated with a gas-filled tank structure of improved construction and requiring a minimum of sealing gaskets.

A more specific object of the present invention is the provision of an improved terminal bushing structure having a spring assembly for maintaining compressive force upon the casing shells of the terminal bushing, the terminal bushing being associated with a gas-filled tank structure and being so disposed or positioned as to require a minimum of sealing gaskets.

Another object of the present invention is the provision of an improved terminal'bushing structure associated with a gas-filled tank in which a compression-spring assembly is positioned at the opposite end of the terminal bushing than is customarily employed in conventional-type terminal bushings.

As well known by those skilled in the art, generally, terminal bushings of the type which exert compressive force along component parts thereof axially of the terminal bushing utilize a cap assembly embodying a plurality of compression springs, which collectively exert compressive force along the terminal bushing components. Such cap structures have, in the past, been provided at the upper end of the terminal bushing exteriorly of the tank structure.

in United States patent application filed January 23, 1959, Serial No. 788,668, now United States Patent 3,057,983, issued October 9, 1962, to Benjamin P. Baker, Russell N. Y eckley and loseph Sueha, and assigned to the assignee of the instant application, there is disclosed and claimed a novel gaseous-type circuit-interrupting structure utilizing a dual-pressure, closed-cycle system, in which it is desired to utilize interrupting gas at high pressure, exhausting this gas, following interruption, into a low-pressure system. Preferably a compressor is provided, which functions to recompress the relatively low-pressure exhausted gas and force it under high pressure back into the high-pressure system. The circuit interrupter of the fore going patent application is of the sulfur-hexafiuoride (SP gas type, and the interrupting effectiveness of this gas is so high that such a type of circuit-interrupting apparatus is suitable for very high-power application.

Associated with a circuit-interrupting apparatus, as set forth in the aforesaid application, is a terminal-bushing structure utilizing the same gas which is present within the tank structure. In the United States patent application filed December 2, 1959, Serial No. 856,775, now United States Patent 3,059,044, issued October 16, 1962, to Robert E. Friedrich and James H. Frakes, and assigned to the assignee of the instant application, there is described a type of gas-filled terminal-bushing structure having a multiplicity of gas-tight seals associated with the spring cap assembly disposed at the upper external end of the bushing. Such a structure requires a number of sealing gaskets and soldered connections associated with the terminal-bushing structure. Obviously, the utilization of a large number of seals increases the possibility of leakage of gas through the seals.

It is a distinct object of the present invention to provide a terminal-bushing construction, associated with a gasfilled tank structure, in which by a novel relocation and repositioning of the component parts thereof, a minimum number of gaskets, subjected to gas pressure and which must be gas-tight, are required. 7

Still a further object of the present invention is to provide an improved gas-filled terminal bushing associated with a tank structure containing electrical components or devices and at least partially gas-filled, in which the spring assembly for maintaining compressive stress on the bushing shells is disposed interiorly or" the tank structure to minimize the number of seals, and in which the springseat elements of the interiorly-disposed spring assembly are so constructed and cooperatively arranged so as to impose cantilever stresses not only on the terminal stud itself, but also on axial wall portions of the contiguous]? disposed interior bushing shell.

Another object of the invention is to provide an improved high-voltage terminal bushing of the foregoing type in which the voltage gradient adjacent the spring assembly is relieved by a novel shielding structure.

Further objects and advantages will readily become apparent upon reading the following specification, taken in conjunction with the drawing, in which:

FIGURE 1 is an end elevational View of a three-pole sulfur-hexaiiuoride (SP gas type of circuit interrupter, to indicate the general type of apparatuswith which the improved terminal-bushing structure of the present invention may be employed; and,

H6. 2 is an enlarged, partially vertical sectional View taken through the improved terminal-bushing structure of the present invention, with nonessential portions broken away, indicating the single seal at the upper end of the bushing which is now required by the new construction.

Referring to the drawings, and more particularly to PEG. 1 thereof, the reference numeral 1 generally designates an electrical apparatus, such as a circuit-interrupting structure, involving a tank structure 2 and end caps 3, 4, out of which may be laterally pulled a circuit-interrupting assemblage 5, which is supported at the lower ends of terminal bushings 6, 7. Disposed at the upper end of the tank structure 2 are a pair of cylindrical support cylinders 11, 12 having upper perforated support plates 3, to which a grounded mounting flange support 9 of the terminal bushing 6, 7 may be secured by bolts 9a.

It will be observed that the cylindrical support portions 11, 12 are welded, as at 13, to the upper side of the tank structure 2. As set forth'in the aforesaid Baker'et a1 patent, preferably sulfur-hexafluoride (SP gas, at a pressure of say 60 p.s.i., is disposed within the tank structure 2. In addition, a high-pressure storage tank 5a is associated withthe right-hand end of the arc-extinguishing assemblage :"a', as viewed in FIG. 2. This high-pressure storage tank releases a blast of gas during the interrupting operation, which is subsequently exhausted into the gen- Patented Dec. 8, 1964 eral interior of the tank structure 2, as set forth in detail in the aforesaid Yeckley et al. Patent 3,057,983.

With further reference to FIG. 2, which shows the novel terminal-bushing construction of the present invention, it is apparent that a tubular metallic terminal stud 14 extends axially through the terminal bushing 7 and has threadedly secured thereto, as at 15, an upper terminalcap casting 16. integrally formed with the terminal cap 16 is an upper line-terminal stud portion 17, to which a line connection may be made. It will be noted that a single seal 18 is provided between the inner side of a recess 21 associated with the cap structure 16 and the upper end surface 22 of a weatherproof casing 23, which is formed of any suitable weatherproof material, such, for example, as porcelain.

Also disposed at the lower end of the outer porcelain shell 23 is a second gasket 18. The two gaskets 18 are preferably of the double concentric o-ring type, involving rubber O-rings and having a sniffer or detecting hole located therebetween, which is generally plugged and is available, at times, during maintenance operations for detecting any gas leakage. Reference may be had to United States patent application, filed November 27, 1959, Serial No. 855,760, now United States Patent 3,066,823 issued December 4, 1962 to Benjamin P. Baker, for information regarding the functioning of the detecting hole 10 and its particular location between the concentric rubber gaskets 18a, 18b.

It will be noted that the upper cap 16 is provided with gas-entrance holes 25, which permit the communication of gas Within the tank structure 2 up through the hollow terminal stud 14 and through the gas holes 25 to the region 26 interiorly o fthe bushing structure 7. As is obvious, the region 26, provided between the inner wall of the casing 23 and the outer surface of the tubular conductor stud 14, is consequently filled with gas at the same pressure as is present within tank 2.

Disposed within the tank structure 2 and positioned below the grounded mounting flange g is a lower casing shell 2'7, which is maintained in compression, as is the upper casing shell 23, by the employment of a compression spring cap assembly, generally designated by the reference numeral 28 in FIG. 2.

The spring assembly 28 includes a plurality of, say for instance six, compression springs 31, which are disposed between a pair of spring plates 32, 33 which have a sliding collar interrelation, as at 34. In the closing and opening operations of the circuit-interrupting assemblage 5, considerable shock forces are present at the ends of the respective opening and closing strokes, and these shock forces impose considerable lateral cantilever stresses upon the lower ends of the supporting terminal bushing studs 14. The sliding collar construction 34 has the important advantages of assisting to transfer cantilever stresses imposed on the interior end of the conductor stud 14 to the wall portions of the shell 27 in compression. As a result, the resistive counter-balancing forces exerted by the wall portions of the lower insulating shell 2? thereby minimize the effect of the aforesaid lateral shock forces upon the terminal studs 14 of the bushings 6, 7. Suitable bolts, not shown, are passed through holes 35 with clearance provided in the lower spring plate 33, and are threaded into tapped holes 36 provided in the upper spring plate 32. Thus, the spring plates 32, 33 are assembled with the several compression springs 23, and the bolts, not shown, under compression, constituting thereby a unitary assembly, which is threaded onto the lower externally-threaded surface of the tubular conductor stud 14, as at ll. When this assembly step has been achieved, the bolts, not shown, are removed, and the spring pressure, exerted by springs 31, operates to slide the upper spring plate 32 upwardly along the sliding collar surface 34, so that compressive force is exerted upwardly along the lower casing shell 27 along the grounded mounting flange 9, the upper casing shell 23, and against the upper terminal cap 16. Ob-

l viously, therefore, the tubular conductor stud 14 is under corresponding tensile stress.

Associated with the lower spring assembly 28 is a voltage shield 42 formed of spun metal such for example as copper, which is brazed, as at 43, to a bronze threaded ring 44, the latter being threadedly secured upon the external lower threaded surface of the conductor stud 14. The voltage shield 32 functions to relieve the voltage stress about sharp corners of the spring assembly 28 and thereby considerably enhances the fiashover value of the bushing as a whole. Following the threading of the ring 1, solder 19 is additionally provided between the ring 44 and the conductor stud 14 for a tight seal and to maintain the position of the voltage shield 42.

It will be observed that by positioning, or relocating the compression-spring assembly 23 so that the latter is positioned in an inverted position to that customarily employed, and being disposed within the interior of the tank structure 2, the seals at the lower end of the terminal bushing '7 are not subjected to any differential pressure, and gas leakage therethrough is unimportant.

There are only required the gas-tight seals 18 at the upper external end of the terminal bushing 7. These constitute only two in number at opposite ends of the weatherproof shell 23. Comparing the number of external seals of the terminal bushing '7 of the present invention with the considerable number, as set forth in the aforesaid Friedrich et al. patent application, which number is live, it is obvious that a distinct improvement in simplicity has been made. This is particularly important when it is desired to retain the gas within the tank structure 2. over long periods of time without any leakage of gas. Moreover, the sulfur-hexafluoride (SP gas is re latively expensive, and it is very important to prevent any leakage whatsoever. By minimizing the number of seals which must be gas-tight, there results a distinct advantage in retaining the gas without the hazard of loss within the tank structure 2.

The improved terminal-bushing construction 6, 7 of the present invention eliminates all soldered joints, decreases the height of the bushing from the mounting flange 9 to the top end of the bushing, uses only one gastight casting 16, reduces to a minimum the number of gas-tight joints required, gives a more pleasing appearance, is less expensive and more trouble-free than prior bushing designs.

Although the present invention has been shown as embodied in circuit-interrupting apparatus of the type set forth in the aforesaid Baker et al. patent application, it will be clear that the present invention is also applicable to any electrical apparatus associated with a tank structure, which is at least partially filled with an insulating gas. Transformer installations are a further application of the present invention. Merely for purposes of illustration has the present invention been shown as applied to a circuit-interrupting apparatus.

Although there has been shown and described a specific electrical apparatus, it is to be clearly understood that the same was merely for the purpose of illustration, and that changes and modifications may readily be made therein by those skilled in the art without departing from the spirit and scope of the invention.

We claim as our invention:

1. The combination with gas-filled electrical apparatus of a terminal bushing, said terminal bushing being mounted upon a tank structure containing the electrical apparatus, said terminal bushing including a conductor stud and a pair of easing shells and an interposed groundilange mounting plate, a spring cap assembly disposed at the interior end of the terminal bushing within the tank structure to maintain the several component parts of the terminal bushing under pressure, said spring assembly including a pair of spring plates having sliding, collar portions surrounding the terminal stud and telescopically moving over each other, one spring plate substantially abutting the interior end of the enclosed casing shell, and the lowermost spring plate being fixedly secured to the interior end of the terminal stud, whereby cantilever stresses imposed upon the conductor stud are transmitted through the sliding collar portions of the spring plates to the enclosed casing shell.

2. The combination of claim 1, wherein a cup-shaped voltage-shielding member encloses the spring assembly and is interposed between said one end of the enclosed casing shell and said one spring plate.

3. The combination of claim 2, wherein the inner periphery of the cup-shaped voltage shielding member is fixedly secured to the interior end of the conductor stud.

References Cited in the file of this patent UNITED STATES PATENTS Jansson Feb. 14, 1933 Hillebrand Dec. 4-, 1934 Leeds et &1 Apr. 25, 1961 Friedrich et al Oct. 16, 1962 FOREIGN PATENTS Sweden Oct. 13, 1925 Canada Sept. 15, 1959 Australia May 28, 1959 Great Britain July 20, 1960 

1. THE COMBINATION WITH GAS-FILLED ELECTRICAL APPARATUS OF A TERMINAL BUSHING, SAID TERMINAL BUSHING BEING MOUNTED UPON A TANK STRUCTURE CONTAINING THE ELECTRICAL APPARATUS, SAID TERMINAL BUSHING INCLUDING A CONDUCTOR STUD AND A PAIR OF CASING SHELLS AND AN INTERPOSED GROUND FLANGE MOUNTING PLATE, A SPRING CAP ASSEMBLY DISPOSED AT THE INTERIOR END OF THE TERMINAL BUSHING WITHIN THE TANK STRUCTURE TO MAINTAIN THE SEVERAL COMPONENT PARTS OF THE TERMINAL BUSHING UNDER PRESSURE, SAID SPRING ASSEMBLY INCLUDING A PAIR OF SPRING PLATES HAVING SLIDING COLLAR PORTIONS SURROUNDING THE TERMINAL STUD AND TELESCOPICALLY MOVING OVER EACH OTHER, ONE SPRING PLATE SUBSTANTIALLY ABUTTING THE INTERIOR END OF THE ENCLOSED CASING SHELL, AND THE LOWERMOST SPRING PLATE BEING FIXEDLY SECURED TO THE INTERIOR END OF THE TERMINAL STUD, WHEREBY CANTILEVER STRESSES IMPOSED UPON THE CONDUCTOR STUD ARE TRANSMITTED THROUGH THE SLIDING COLLAR PORTIONS OF THE SPRING PLATES TO THE ENCLOSED CASING SHELL. 